1. Field of the Invention
This invention relates to a process of manufacturing carbon fibers having increased chemical stability.
2. Prior Art
Ceramic fibers have potential application for fiber-reinforced metal composite material known as FRM or MMC and carbon fiber reinforced ceramics composite material known as CFRCe. These ceramic fibers are not sufficiently resistant to heat, and they are produced for instance by chemical vapor deposition in which silicon carbide is coated over carbon fibers. This method is however disadvantageous in that the resulting coated fiber product is objectionably thick and extremely costly.
Another method is disclosed in Japanese Patent Publication No. 50-29528 in which carbon fiber is heated at least at 800.degree. C. in a gaseous atmosphere containing silicon components so as to provide a silicon carbon region at the outer surface as well as at least part of the inner layer of the fiber.
There is still another method of producing ceramics-coated carbon fiber as disclosed in Japanese Laid-Open Publication No. 63-211368, in which a flock of continuous carbon filaments is coated with a heat-resistant carbide by means of reactive chemical deposition.
The carbon fibers produced by any of the above known methods are not sufficiently resistant to heat and chemicals as they are and hence not suitable for use as satisfactory fiber reinforced metal composite material or fiber-reinforced ceramics composite material.